Note on the demo data

After launching the app, you can log as one of the demo users:

Elena

• email: Elena@example.com
• password: password
• Elena has access to three groups. To demonstrate joing a group, go to Join Group screen and enter code 3 in the textfield. Click the button and you will gain access to the group "Souflé"

  Mateo

• email: Mateo@example.com
• password: password
• Mateo has access to all four demo groups. Group "Choufleur" contains some example expenses

  Frontend

  API Methods using the RestClient

  Kotlin code that allows to post data into the backend

  GET

• get Groups

  LaunchedEffect(Unit) {
      RestClient.instance.getGroups(object : GroupsCallback {
          override fun onSuccess(groups: List<Group>) {
              receivedGroups = groups
              Log.d("RestClient", "GET groups success $receivedGroups")
          }
  
          override fun onFailure(error: String) {
              Log.d("RestClient", "GET groups error $error")
          }
      })
  }

• get Users

  LaunchedEffect(Unit) {
      RestClient.instance.getUsers(object : UsersCallback {
          override fun onSuccess(users: List<User>) {
              receivedUsers = users
              Log.d("RestClient", "GET users success $receivedUsers")
          }
  
          override fun onFailure(error: String) {
              Log.d("RestClient", "GET users error $error")
          }
      }, selectedGroup!!.id)
  }

• get expenses

  LaunchedEffect(Unit) {
          RestClient.instance.getExpenses(object : ExpensesCallback {
              override fun onSuccess(expenses: List<Expense>) {
                  receivedExpenses = expenses
                  Log.d("RestClient", "GET expenses success $receivedExpenses")
              }
  
              override fun onFailure(error: String) {
                  Log.d("RestClient", "GET expenses error $error")
              }
          }, selectedGroup!!.id)
      }

• get debts

  LaunchedEffect(Unit) {
        RestClient.instance.getDebts(object : DebtsCallback {
            override fun onSuccess(debts: List<Debt>) {
                receivedDebts = debts
                Log.d("RestClient", "GET debts success $receivedDebts")
            }
  
            override fun onFailure(error: String) {
                Log.d("RestClient", "GET debts error $error")
            }
        }, group!!.id)
    }

  POST

• create a new group

  LaunchedEffect(Unit) {
  RestClient.instance.createGroups(listOf("1", "2"), "TestGroup", "EUR", "description" )
  }

  -> description is optional

• delete group

  LaunchedEffect(Unit) {
  RestClient.instance.deleteGroup("4")
  }

• add Users to Group

  LaunchedEffect(Unit) {
  RestClient.instance.addUsersToGroup("4", listOf("2", "4"))
  }

• remove Users from Group

  LaunchedEffect(Unit) {
  RestClient.instance.removeUsersFromGroup("0", listOf("2", "4"))
  }

• add Expenses to a group

  LaunchedEffect(Unit) {
  RestClient.instance.addExpense("0","1", listOf("1","2"),25.2, "2023-11-18T21:16:26.567Z", "for beers")
  }

  -> description is optional

  Backend

Run

To run backend move to the backend directory and run

npm run start

This will run a server listening on localhost:3000

One group with four users is hardcoded.

REST API requests

Backend exposes methods (example body provided for post methods):

• POST http://localhost:3000/groups/{groupId}/expenses

{
  "payerId": "1",
  "participantsIds": ["1", "2", "3", "4"],
  "amount": 100,
  "date": "2023-11-18T21:16:26.567Z",
  "description": "For beers"
}

• GET http://localhost:3000/groups/{groupId}/expenses
• GET http://localhost:3000/groups/{groupId}/debts

Debts are calculated automatically based on expenses, thus no POST debts method is possible.

• GET http://localhost:3000/groups
• POST http://localhost:3000/groups

{
  "userIds": ["1", "3"],
  "name": "group 1",
  "description": "test group"
  "currency": "EUR"
}

• DELETE http://localhost:3000/groups/{groupId}
• PUT http://localhost:3000/groups/{groupId} -> modify group (right now only by adding users)
• GET http://localhost:3000/groups/{groupId}/users

{ "userIds": [1, 4] }

To be implemented:

• Create a user
• (Optionally) optimize number of debts (quite complicated algorithm based on graph search, read more on Splitwise simplification feature)